Production of soap



' Patented Aug. 28, 1945 PRODUCTION or soar Walter Russell Trent, NorthArlington, N. J., as-

signor to Coigate-Palmolive-Peet Company, Jersey City, N. J acorporation of Delaware No Drawing. Application March 25, 1942, SerialNo. 436,098

7 Claims.

The present invention relates to processes for making soaps and, moreparticularly, to processes of preparing soaps from mono-fatty acidesters.

Soaps have been made from time immemorial by saponification of fats andoils. The saponification is generally carried out by intimately mixingsuch fats and oils with alkaline agents in such proportions as arereadily determinable by those skilled in the art. The mixture is heatedwith agitation, forming soap and glycerine. After completion of thereaction, the soap is salted out, leaving glycerine in solution which isthus separated from the soap. If more of the glycerine is to be removed,successive washings, resulting in considerable aqueous dilution of theglycerine,

must be employed. The soap is put in a crutcher, where it is mixed withany desired adjuvant material, and may then be framed or plodded andcut, or run in a plastic condition to steel rolls for flaking. Theflakes may be left in this condition or may be ground. The plastic soapmay also be forced through a nozzle in a spray tower to form beads orother finely divided particles. Continuous or semi-continuous processesof soap-making have been provided, but high temperatures and/ ornumerous washings are also employed in these for removing 'glycerinefrom the soap.

Recently, it has been taught to split fats or oils by hydrolysis withwater to obtain free fatty acids, and then to saponify these acids. Freeacids react very quickly and vigorously with alkaline agents, ascompared with the long process of saponifying fats and oils, but it isdiflicult to control the reaction and the condition of the product atthis speed. Contact of free fatty acids, particularly unsaturated acids,with air, even at moderate temperatures, causes the formation of darkoxidation products which tend to discolor soaps. Furthermore, the use offree acids requires that expensive, corrosion-resistant equipment beemployed.

It is an object of the present invention to provide a rapid andeconomical process for making soaps, wherein lower alkyl mono-fatty acidesters are employed.

It is another object of the invention to provide a novel process ofmanufacturing soap of controlled water content.

It is also an object of this invention to provide a novel and improvedmethod for the continuous manufacture of soap from fatty acid esters oflower monohydric alcohols.

The invention also contemplates the provision of a novel process for thepreparation of soap in granular, globular or other comminuted' forms. 4

According to this invention, soap is prepared by mixing a fatty acidester of a lower monohydric alcohol with an alkaline or saponifyingagent, the ensuing reaction being carried out at reduced pressures toremove alcohol from the product as the alcohol is liberated in thereaction. The reaction is preferably carried out as a continuousprocess, operating from a continuous method of producing monoesters byalcoholysis of fats and fatty oils, using a measuring or proportioningdevice for mixing the monoesters with the alkaline agent in suchproportions as are determined by the operator, and then continuouslypassing them to a saponifier, as will be described in more detail infra.

In selecting fatty acid esters for use in the present invention, it ispreferred to employ fatty acid esters of short chain monohydricalcohols, especially" of alcohols having a boiling point in the presenceof excess water of lower than C.

at atmospheric pressure,.and preferably the lower alcohols having 1 toabout 6 carbon atoms to the molecule. By excess water is meant water inexcess of the azeotropic composition of the alco hol with water. Thefatty acids are preferably those having about 12 to about 20 carbonatoms, and mixtures of the esters may also be used.

Mono-fatty acid esters of polyhydric alcohols may also be present inadmixture with monohydric alcohol esters. Esters satisfactory for use inthe process of the present invention include ethyl laurate, methylstearate, ethyl margarate, propyl oleate, ethyl esters of coconut oilfatty acids, isopropyl esters of tallow fatty acids, methyl esters oftall oil fatty acids, :butyl palmitate, tertiary butyl laurate, methylarachidate, amyl myristate, isobutyl esters of cottonseed oil fattyacids, benzyl palmitate, and other monohydric alcohol esters. Among themonoesters of polyhydric alcohols which may be present in admixture withthe esters of monohydric alcohols are ethylene glycol monostearate,propylene glycol monolaurate, trimethylen-e glycol monoesters of oliveoil fatty acids, glyceryl alpha- (or beta-) monostearate, mannitolmonoesters of coconut oil fatty acids, sorbtol monopalmitate, erythritolmono-oleate, etc.-

Any of these monoesters may be mixed with di-, tri-, or polyesters fortreatment in accordance with this invention, although such modificationis not preferred.

The alkaline or saponifying agents which may be used forsaponifyingthese esters include sodium and potassium hydroxides,carbonates, silicates, etc., pyridine, methyl morpholine, piperidine,alkyl amines, alkanolamines and other organic and inorganic bases andalkaline materials, and mixtures of these. The alkaline agent may beintroduced in aqueous solution, in alcoholic solution, or in'solutionsof other solvents, or may be substantially anhydrous and/orsubstantially undiluted. The amount of solvent introduced with thealkaline or saponifying agent has may alone be sufilcient to raise themixture to the desired temperature, depending upon the materialsemployed and subsequent operating conditions, or heat from externalsources may be supplied. Either or both of the reactants may bepreheated by steam or other means before being run into the vesseland/or the mixture may be heated during and/or after admixture. Soap andalcohol are thereby formed, and the alcohol is volatilized at thetemperature and reduced pressure within the vessel and is withdrawn.

The operation 'of this process can be carried out continuously bycontacting a monoester with a saponifying agent under conditions oftemperature and subatmospheric pressure adapted for saponification ofthe ester and removal of the liberated alcohol. The temperature of thesaponification mixture may bevaried over a Wide range, depending uponthe type of ester to be saponified, the amount of water and/or othersolvent present, and the type of product desired. Even at only slightlyelevated temperatures, the reaction rates are relatively high, ascompared with polyesters, such as fats and oils. The temperatureemployed is partially controlled by the degree of vacuum used, and bothtemperature and pressure are influenced by ,the boiling point of thealcohol to be liberated in the reaction. Thus, depending upon the esterto be saponified and the pressure employed, elevated tempera tures ofabout 20 to about 100 C. can be used. At these temperatures, products ofvery light color are obtainable. Moreover, the reaction may be carriedout in the presence of air, as the neutral esters are substantiallyundarkened by this treatment.

The monoester and alkali, preferably preheated to a desired temperature,are automatically proportioned and delivered, preferably continuously,to a mixing vessel where the ester is saponified under reduced pressure.The mixing vessel may be supplied with heat transfer means, such' as ajacket, for heating or cooling, as required, and the solvent for thealkali, as well as the alcohol liberated by the reaction, is vaporizedunder the reduced pressure and is removed from the mixing vessel.Regulation of the temperature of the reaction mass is a factor indetermining the amount of solvent and/or alcohol remaining in theproduct. The soap, dried or partially dried, can be removed from themixing vessel and cooled.

Various means may be employed for facilitating the reaction of thesaponifying agent with the ester. Thus, it has been found convenient tojet the alkaline solution into the liquid ester and to employ a size andshape of reaction vessel which provides a high degree of turbulence forcontacting the materials. The vessel may be in the form of a conduit andmay be equipped with a screw conveyor to displace solid material formedwhen using plastic or viscous mixtures.

The reaction vessel may also be operated in conjunction with a spraytower 01! other. means for obtaining substantially granular and/orhollow particles, the material from the reaction v ssel being forced inplastic form to a spirmer bowl or spray nozzle, and, upon atomization,coming in contact in the tower with a current of inert gas, preferablyair. The air current may be heated and it is preferably passed throughthe tower countercurrent to the sprayed material, although concurrentpassage of the air is also contemplated.

In vaporizing the hydroxylated products of the reaction, thesaponification of the monoesters afiords great advantage oversaponification of the glycerides or other natural esters, since thealcohols liberated can be vaporized for recovery at much lowertemperatures and with far less difficulty than is possible withglycerine. Where the reactants employed are nearly anhydrous,considerably lower temperatures can be used for removal of solvent thanare possible with soap made from even free fatty acids, as the loweralcohols, including methyl, ethyl, propyl and isopropyl alcohols, can bevaporized below the temperature required at a given pressure for thevaporization of either water or glycerine. Since the lower alcoholliberated is lower boiling in the presence of sufilcient water thanglycerin and/or water and requires less heat to volatilize, lowertemperatures may be used, and lighter colored products are consequentlyobtainable.

Another advantage of the present process is that, wherethe reaction isnot carried to completion, there is no rancidity problem arising fromthe presence of unreacted mono-fatty acid esters in the soap products,as is the case with unreacted fats or fatty acids. A proportion of themono-fatty acid ester can be left unreacted in the product to provide asuperfatting agent therein, and such unreacted residues providesuperior, more stable and sweeter-smelling superfatting materials thanare the fats and oils disclosed by the prior art. By operating at lowtemperatures, the excess fatty acid ester can be left in the soap, eventhough substantially all of the liberated alcohol is volatilized.

The moisture or solvent content of the finished I product can bemodified by regulating the heat the reactants and/or furnishing heat tothe reaction vessel from an external source, or otherwise. Thetemperature required is far below that necessary for glycerine recoveryin saponi-fying glycerides. Therefore, although possible, it isunnecessary and less desirable to go to the temperature of moltenanhydrous soap or higher in order to vaporize the monohydric alcoholsliberated, as they or their aqueous azeotropes are lower boiling thanwater. Furthermore, it is possible to recover the soap in hydrated form,but free from the alcohol, without additional hydrating equipment, asrequired with anhydrous soap obtained in certain methods of saponifyingglycerides. Moreover, shorter periods of heating, with consequentlydiminished danger of local overheating and decomposition, can beemployed.

Soap builders, inert materials, anti-oxidants, etc., may be added to themonoester and/or to the saponifying agent before contacting. Since thewashing steps, in general use in prior art' practice, need not beemployed, these modifying agents, even if water-soluble, are found inthe product of the present process. Converse it is also possible toemploy, if desired, vol e, waterinsoluble materials, such as low-boi gpetroleum hydrocarbons, the presence of w ch in the final product mightbe disadvantageous for some uses,

and of the pressure upon the condensers.

since they do not appear in' the finished product.

Certain saponification accelerators, while not ordlnarily required forsaponifyirig monohydric al cohol esters, fall in this category and maybe added, if desired.

The vaporized water or other solvent and the vaporized alcohol liberatedin the reaction are withdrawn at the top of the reaction vessel andtogether pass to a condensation system. The temperature of the vesseland of the passage to the condensers is maintained above the dew pointof the vapors. v condensed, but it is'preferred to provide at least onecondenser for each material to be condensed or to employ a fractionatingcolumn. The condensers may be of reflux, jet or other suitable type. Therecovery of solvent and/or alcohol in relatively pure condition isfacilitated by this means.

The pressure within the vessel is easily regulated by control of thecondenser temperatures The pressure within the reaction vessel ispreferably low enough to provide rapid vaporization of the highestboiling material to be withdrawn as a vapor.

In practice, temperature and pressure conditions can be so regulatedthat a dry product or a hydrated product can be produced. The productmay be made in a moreor less finely divided condition, which permits itsready transformation into flakes or other physical forms, for example,by passing between a pair of properly spaced rolls, or by pressing intocakes, or by other means, with or without addition agents.

Adjuvant materials may be admixed with the soaps thus formed by mixingthem with the mono.- esters and/or the saponifying agents beforecontacting, by simultaneously passing into the reaction vessel asolution containing such adjuvant materials, and/or by mixing the finalproduct therewith. Such adjuvant materials may include fatty acid soapsprepared b the same or other methods, resin acid soaps, naphthenic andalkylated naphthenic acid soaps, sulphated and sulphonated organiccompounds, alkaline Soap builders, water-soluble, water-softeningcompounds of the acids of phosphorus, and other salts, including sodiumcarbonate, sodium silicates, trisodium phosphate, borax, sodiumtetraphosphate,

sodium bicarbonate, sodium sulphate, sodium chloride, sodium acetate,sodium hypochlorite, sodium thiosulphate, sodium penborate, sodiumtartrate, sodium citrate and sodium oxalate, and the correspondingammonium, substituted ammonium and potassium salts of the correspondingacids; insecticidal, germicidal, styptic and me- I dicinal agents,including aluminum chloride, mercuric chloride and various copper andlead salts; coloring agents, abrasives, fillers, and water-dispersiblegums, including dyes, lakes, pigments, silica, kieselguhr, silica gel,feldspar, precipitated chalk, pumice, infusorial earth, bentonite, talc,starch, Irish moss, sugar, methyl cellulose, agar, gum tragacanth,gum'arabic and polyvinyl alcohol; liquids, such as ethyl alcohol,glycerol, cyclohexanol, naphtha, benzene, kerosene, turpentine, pineoil, decalin and tetralin and the like. The type of addition agent willdepend upon the ultimate use of the new composition. Y v

The reaction mixture from the s'aponification vessel may be dischargedtherefrom into a cooling element or conduit, where it is partiallycooled, thus partly solidifying the soap. It maythen be passed to anextrusion orifice, where it ma be cut into bars. During the coolingoperation but The vapors may be conjointly while the soap product isstill liquid due to the presence of water and/or other solvents, anydesired modifiers oradjuvant materials, as aforesaid, includingbuilders, abrasives, perfumes, coloring principles, germicides, liquids,air or other gas, etc., may b injected into the soap. The regulation ofthe supply of cooling fluid, both in amount and temperature, is alsodesirable for controlling the amount of solvent (including water)remaining in the soap. Solvent vapors (and any remaining alcohol)produced in the re action vessel are condensed, wholly or in part, inthe cooling element.

In practice, when producing bars and cakes of soap, it is preferred soto control the cooling of the soap in the cooling element that the soapis at least partially liquid upon passing to the extrusion element. Thiselement, having an orifice of cross section approximating that of thedesired soap cake; is preferably of extended length and jacketed forcarrying a cooling fluid for further cooling of the soap The cooling ofthe soap may thus be substantially completed in the extrusion orificeduring its passage therethrough.

Where a fatty acid ester of an alcohol having a boiling point above thatof water and/or where a solvent for the saponifying agent having aboiling point above that of water is employed in the material undertreatment, it will be understood from the foregoing that at'least partof such alcohol and/or solvent can be retained, if desired, in asubstantially anhydrous soap. The temperature (or vacuum) in thereaction vessel, for example, can be lowered enough so that all of suchalcohol and/or solvent is not vaporized but a portion falls out with thesoap. The temperature selected is higher than the boiling point of waterat the particular pressure in the vessel but lower than the boilingpoints of the alcohol and/or solvent. Similarly, where the fatty acidester of a low-boiling alcohol is used, the temperature and pressureconditions in the reaction vessel can be regulated so as to removesubstantially all of the liberated low-boiling alcohol,'

while retaining at least part of the water or other solvent.

The soap may be passed to drum dryers to produce flakes and ribbons.Since drying can be accomplished by other means, as set forth herein,chilling rolls may instead be provided. Where it is desired to form afriable soap, sudden chilling has been found to be advantageous. Thedryer soaps are more friable than those containing considerable amountsof water, and very dry soaps are frequently self-disintegrating,

breaking up into small grains upon cooling.

Thus, after removal of alcohol and water or other solvent in thesaponification vessel, the soap may be withdrawn by means of scaledconveyors, preferably operated under subatmospheric pressure. Theconveyors may be jacketed, and a plurality of jackets may be employed,so that a heating fluid may be passed through the first part of thejacket (to aid in maintaining a sufficiently high temperature within thesaponification vessel), while the second part carries a cooling fluid togive the soap a sudden chill. Another and/or additional means ofsuddenly cooling may be employed by injecting water directly into thesoap while in the conveyor, preferably at a part of the conveyornon-contiguous to the outlet of the reaction vessel.

While the removal of alcohol formed with the soap acts to cool the soapby the evaporation of the alcohol in the reaction vessel, additional wa-.the condensers.

ter or other liquid may be injected into the soap at temperatures abovethe boiling point of such injected liquid at the reduced pressure in thereaction vessel, the vapors being removed as formed so as not to hydratethe soap. For example, water introduced into the soap in the conveyor isimmediately vaporized at the temperature of the soap, cooling the soapat a low pressure and in the absence of air, and the water vapor may bepassed into the reaction vessel, if desired, for removal with the vaporstherein to If it is desired to hydrate the soap to any degree,additional water may be injected into the soap, either while in theconveyor or farther along, controlling th amount injected. The coolingjacket can be employed for condensing vapors before discharge. Evenwhere considerable hydration is desired and sufllcient cooling can beobtained by circulating a cooling fluid in a conveyor jacket, it maynevertheless be advantageous to vaporize part of the injected water forthe purpose of obtaining. uniform distribution of the water added. Suchuniformity may also be obtained by agitation in the conveyor. Economy ofoperation may be achieved by using one of the reactants, preferably themonoester, as the cooling fluid in the jacket. This serves to preheatthe reactant before its passage to the saponification vessel.

The following examples described herein are merely illustrative of thepresent invention, and it will be understood that thisinvention is notlimited thereto.

Example 'I About 200 gallons per hour of the ethyl esters of coconut oilfatty acids are continuously contacted with about 106 gallons per hourof 30 B. sodium hydroxide solution, and at the same time process steamis injected to raise the temperature of the mixtureto about 60 C. Themixture is passed through a short length of pipe with reverse bends toprovide good mixing and into a 1 reaction vessel undera vacuum of 20inches of mercury. The temperature is maintained at about 80 C., and theethyl alcohol formed is withdrawn at the top of the vessel. The resultinsoap product is continuously removed through a sealed port at thebottom.

Example II About 350 pounds per hour of the amyl esters of garbagegrease fatty acids are preheated to about 50 C. and passed into areaction vessel having efficient agitating means and under a vacuum ofabout 20 inches of mercury. About 230 pounds per hour of a 28 B.solution of caustic potash at about 60 C. is fed into the vesselconcurrently with the esters. Amyl alcohol is liberated by the reactionand comes off as its aqueous azeotrope. The soap formed is removed by asealed conveyor. v

Although the present invention has been described with reference toparticular embodiments and examples, it will be apparent to thoseskilled in the art that variations and modiflcations'of this inventioncan be made and that equivalents can be substituted therefor withoutdeparting from the principles and true spirit of the invention. Suchvariations and modifications are believed to be within the scope of thepresent speciflcation and within the purview of the appended claims.

I claim:

aasaoso 3. The process for producing soap which comprises reacting afatty acid ester of an alcohol having a boiling point in the presence ofwater in excess of the azeotropic composition of lower than 100 C. atatmospheric pressure with an aqueous solution of a saponifying agentunder reduced pressure and at a temperature above the vaporization pointat said pressure of the free monohydric alcohol in the presence of waterin excess of the azeotropic composition to produce a reaction mixturecomprising a soap and a free monohydric alcohol, thereby removing atleast part of the monohydric alcohol and at least part of the watertherefrom during the reaction.

4. The process for producing soap which comprises preheating at leastone of a fatty acid ester of a lower alkyl monohydric alcohol and asaponifying agent, and reacting said ester with said saponifying agentto produce a soap and a free monohydric alcohol, said reaction beingcarried out under sufficiently reduced pressure to remove the alcohol asit is liberated in the reaction.

5. The process for producing soap which comprises preheating at leastone of a fatty acid ester of a lower alkyl monohydric alcohol and asaponifying agent to a predetermined temperature, re:-

.acting said ester with said saponifying agent under reduced pressureand at a temperature above the vaporization point at said reducedpressure of the free monohydric alcohol whereby a reaction mixturecomprising a soap and a free monohydric alcohol is produced and themonohydric alcohol is removed from said mixture as it is liberated inthe reaction.

6. The process for producing soap of predetermined moisture contentwhich comprises reacting a fatty acid ester of a lower alkyl monohydricalcohol with an aqueous solution of a saponifying agent under reducedpressure to produce a reaction mixture comprising water, soap and freemonohydric alcohol, maintaining the temperature of the mixture duringreaction above the vaporization point at said reduced pressure of thefree monohydric alcohol in the presence of water in excess of theazeotropic composition to volatilize free monohydric alcohol therefrom,and regulating the heat supplied to the reaction mixture, to

produce a soap containing a predetermined proportion of moisture.

7. The process for producing soap. which comprises continuously passinga fatty acid ester of a lower alkyl'monohydric alcohol and a saponifyingagent through a zone at subatmospheric pressure and at a temperatureabove the vaporization Pint' at said pressure of the free monohydricalcohol to produce soap and free monohydric alcohol, continuouslyremoving volatilized monohydric alcohol from said zone, and continuouslywithdrawing soap from said zone.

WALTER RUSSELL TRENT.

